Absorbent pad



A. A. BURGENI ABSORBENT PAD Feb. 10, 1970 m m/A Mw w United StatesPatent O 3,494,362 ABSORBENT PAD Alfred A. Burgeni, Short Hills, NJ.,assignor to Johnson & Johnson, a corporation of New Jersey Filed May 1,1967, Ser. No. 635,161 Int. Cl. A61f 13/20; B32b 3/28, 3/30 U.S. Cl.12S-290 3 Claims ABSTRACT OF THE DISCLOSURE This application disclosesabsorbent, fibrous bodies consisting essentially of short, cellulosicfibers such as comminuted wood pulp fibers and cotton linters, whichpads are given form stability and fluid transfer properties by havingincorporated therein an insert of the same short, absorbent, cellulosicfibers, which insert is longitudinally wet embossed and transverselycorrugated.

BACKGROUND OF THE INVENTION This invention relates to an absorbent padand more particularly, is directed to an absorbent, fibrous bodyconsisting essentially of short, absorbent, cellulosic fibers which canbe used as an absorbent component in sanitary napkins and similarproducts for absorbing body fiuids.

Short, absorbent, cellulosic fibers such as comminuted wood pulp fibersand cotton linters, whose lengths are in the region of about 2millimeters, are low in cost and readily available. They areparticularly suitable for use las absorbent components in numerousabsorbent articles in the form of thick bats or plies because such batshave high bulk and volume and rapidly adsorb fiuids. However, bats ofsuch fibers are unstable due mainly to the shortness of the fiberlength. 'Ihey are tenuous and have low cohesive and tensile strength, donot retain their shape and volume when compressed or moistened, and havelow capillary attraction and low fluid retentivity. When a bat of suchfibers is saturated with fluid, it mats, becomes distorted and fallsapart readily. When incorporated into an absorbent pad, such as asanitary napkin, it has been common practice to include with such batsother components such as gauze, paper, or high bulk wadding to impart tothe napkin form and structural stability and desired fiuid fiow andfluid absorbency characteristics. A sanitary napkin without theseadditional components lacks form and structural stability `and isdistorted readily in use upon the absorption of fiuid.

The fiuid absorption and fluid flow characteristic of bats of wood pulpfibers and like short, cellulosic fibers, while suitable in somerespects, are unsatisfactory in others. When fiuid is applied to thesurf-ace of ra bat of such fibers, it penetrates the bat rapidly andstrikes through to the bottom surface. The fluid absorbed remainsessentially confined in the part of the bat directly under the area ofapplication, i.e., it is not distributed laterally through the bat toany appreciable extent. Due to the low capillarity of lthe bat, itbecomes quickly saturated with fiuid in the region of application andits full absorbent capacity is not utilized. When a plurality of suchbats is used, the bats still have poor fiuid fiow and fluid absorbencycharacteristics and, in efiect, act as a single bat.

Attempts to overcome the problems noted above have includedincorporating spacing elements and separate elements of paper, wadding,and other like materials having higher densities and capillarities thanthe bats of wood pulp fibers `and like short, absorbent, cellulosicfibers so as to aid in the distribution of fiuids. Also, multiple pliesof bats of short, absorbent, cellulosic fibers which have had elongated,compressed patterns embossed therein have been used in such absorbentpads to form channeling areas ice also to aid in the distribution offluids. However, in the first instance, in addition to increasing thecost of m-anufacture of such pads, the inclusion of such high densityelements produced only moderate improvements in the structural stabilityof the pad, and did not effectively solve the problem of dispersing andstoring the absorbed fiuid safely within predetermined channels. In thesecond instance, the embossed plies of short, absorbent, cellulosicfibers, while greatly aiding in the dispersion and safe storage of thefluid, did not fully provide the form and structural stability that isdesirable in the pad. Accordingly, in both instances, the padscontaining or consisting of short, absorbent, cellulosic fibers stillpossessed to a greater or lesser degree in herent disadvantages, and thefunctional potential of such fibers had not been fully utilized.

SUMMARY OF THE INVENTION -In `accordance w-ith this invention, absorbentproducts, such as sanitary napkins, having as an inner core thereof, oneor more normally unstable fibrous bats consisting essentially of short,absorbent, cellulosic fibers suc=h as comm-inuted wood pulp fibers,cotton linters, and the like, are provided with form and structuralstability and improved fluid iiow and fluid absorbency characteristicsby incorporating within said inner core a fibrous insert also consistingessentially of such short, cellulosic fibers, which insert is providedwith transversely spaced, longitudinally extending, wet compressed areasand further, is corrugated in its longitudinal cross section, saidcorrugations being compressed to a lesser extent than said wetcompressed areas, except where said corrugations are traversed by saidcompressed areas. The absorbent products of the invention as contrastedto like products which do not have incorporated therein the improvedinternally disposed fibrous insert of the invention, have increasedcapillarity, increased fiuid retentivity and provide increasedstructural stability to the fibrous core of the absorbent productparticularly in the transverse direction.

The invention contemplates an absorbent product consisting mainly of afiuid pervious cover and an absorbent,

core consisting essentially of short, absorbent, cellulosic fibers ofabout 2 millimeters in length. Disposed within said inner core andconsisting also of said short, cellulosic fibers is a fibrous insertthat is provided with transversely spaced, longitudinally extending, wetcompressed areas to direct absorbed fluid lengthwise through the coreWhile at the same time imparting longitudinal stability to the core.Further, the insert is corrugated in its longitudinal cross sectionwhich serves, to a certain extent, to direct absorbed fiuid transverselythrough the core and to impart a great degree of transverse stabilitythereto. The corrugations of the fibrous insert are compressed to alesser extent than the longitudinally extending compressed areas, exceptwhere the corrugations are traversed by the transversely spaced,longitudinally extending, wet compressed areas.

Referring now, more particularly, to the accompanying drawings and thefollowing description, wherein for illustrative purposes, the inventionis described in connection with a sanitary napkin, the invention will:be even more apparent. It is to be understood, however, that theinvention is not to be limited solely to sanitary napkins, but can beutilized in other products of similar function.

In the drawings:

FIG. l is a perspective view of a sanitary napkin incorporating theinternally disposed, fibrous insert of the invention cut away to revealits interior construction;

FIGURE 2 is an enlarged transverse sectional view of FIGURE l alonglines 2 2;

FIGURE 3 is an enlarged transverse sectional view of FIGURE l alonglines 3 3;

FIGURE 4 is an enlarged perspective view of the absorbent core of thesanitary napkin of FIGURE 1 with the upper layer of fibrous materialpeeled back to reveal in more detail the fibrous insert of the presentinvention and its relationship to the fibrous core of a sanitary napkin;

FIGURE 5 is a partial, longitudinal cross sectional view of FIGURE 2along lines 5--5;

FIGURE 6 is a partial perspective View of the fibrous insert of thepresent invention; and

FIGURE 7 is an enlarged transverse sectional view similar to FIGURE 2but wherein the fibrous insert extends laterally to the edges of thefibrous core of the sanitary napkin to form one variation within thescope of the present invention.

One -form of an absorbent pad, a sanitary napkin 10 incorporating theinvention is illustrated in FIGURES l-5 and includes a relatively thickelongated absorbent core 12 enclosed within a liquid pervious wrapper 14whose ends extend beyond the ends of the absorbent core to provide theusual attachment tabs 16. The absorbent core is about 21/2 inches wideand 8 inches long and consists of a bottom layer 18 of comminuted woodpulp fibers about 716 inch thick and weighing about 50 grains (8 grainsper cubic inch). Positioned internally of the absorbent core 12 betweenthe bottom layer 18 and the top layer 20 is a lbrous insert 22 which isabout 6 inches long, 13/8 inches wide and averages about 1A inch inthickness7 and its placement is approximately equidistant from the frontand rear ends of the absorbent core 12 as well as from the edges of theabsorbent core 12. The entire assembly is enclosed within the liquidpervious wrapper 14,.

A thin, flexible film 28 of polyethylene, approximately 1/a mil thick,is positioned intermediate the liquid pervious wrapper 14 and the pulpor fluff layer 18 and covers the bottoms and sides of the absorbentcore. The top surface of the absorbent core which is not covered by thefilm is the surface which is placed against the tbody when the napkin isworn to absorb uid which impinges upon it.

The fibrous insert 22 that is positioned internally of the absorbentcore 12 is made of the same short, cellulosic Iwood pulp fibers as isthe core 12 and weights approximately 50 grains (an average bulk densityof about 241A grains per cubic inch). The insert 22 is formed withtransversely spaced, longitudinally extending, wet compressed areas 30and transverse corrugations 32 to provide a structure that is corrugatedin longitudinal cross section. (See FIGURE 5.) In the embodiment shownin the drawings the longitudinally extending compressed areas 30 areabout 2 millimeters wide and are transversely spaced from one another adistance of about 2.7 millimeters. The described construction is apreferred one, and it will be understood that many variations thereofare possible without departing from the `principle of the construction.The number and width of the embossing lines, for example, may be reducedor increased, and instead of forming a pattern of discrete, equidistant,embossing lines, insert 22 may be uniformly compressed across its totalwidth or a part thereof. References made hereinafter to embossing ortransversely spaced, compressed areas refer to any and all embossingpatterns, including uniform Compression across the width of the insert.

The longitudinally compressed areas 30 and transversely extendingcorrugations 32 are formed in the insert 22 by first spraying one orpreferably both surfaces of the bat of comminuted wood pulp fibers withabout 0.003 ml. of water per square centimeter of web surface. The waterspraying techniques and skin formation in bats of short, cellulosicfibers are set forth in greater detail in my United States Patent Nos.2,955,641 and 3,017,304 and need not be repeated here,

Subsequent to being wetted, the moistened lweb is passed beneathcompressing rollers having circumferential ribs transversely spacedthereon to form the densified compressed areas 30 in the moistened web.The amount of compression applied by the compressing rollers cangenerally be varied over a range of from about 10 to about 5() poundsper square inch.

Immediately following the formation of the transversely spaced,longitudinally extending, densified compressed areas 30 in the moistenedfibrous bat, it is passed between transversely extending corrugatingrollers adapted to intermesh with sufficient spaces providedtherebetween so as to impart less compression to the moistened web thanwas applied thereto in forming the transversely spaced, longitudinallycompressed areas 3f).

Generally, the pressure applied to the moistened web by the corrugatingrollers need only be sufficient to set the corrugation 32 therein andaccordingly, can range from about 1.5 to about 7 pounds per square inch.

Following the embossing and corrugating of the fibrous insert, it isthen permitted to dry or is dried by the application of heat whichcauses the fibers to set thereby providing a distorted web of short,cellulosic fibers with form stability, particularly in the transversedirection.

The distorted web of short, cellulosic fibers from which the insert 3)is made is then led into a cut-off mechanism and cut into appropriatelengths. In the embodiment of the sanitary napkin described above, thedistorted web is cut into lengths of about 6 inches and is then laiddown centrally on top of a substantially uncompressed web of Short,cellulosic fibers from which the lower layer 18 of the sanitary napkinis to be formed. The lengths of embossed and corrugated web are spacedlongitudinally on the uncompressed fibrous web and are then covered byanother substantially uncompressed fiber web which will ultimately formthe upper fibrous layer 2t) of the core 12 of the sanitary napkin 1li.The thus joined webs 18, 22 and 2t) are then fed into a cut-offmechanism where they are formed appropriately into individual pads 12.Preferably, the pads will also have placed on the lower surface thereof,extending up over the sides, a thin polyethylene sheet 28 whichultimately will form a fluid impervious barrier on the side of thenapkin adapted to be worn away from the body. This whole assembly thenis wrapped in the usual manner in a cover 14 with longitudinallyextending tab portions 16 forming the usual attachment tabs of thesanitary napkin.

In the embodiment shown in FIGURES 1 through 4 it is noted that thefibrous insert 22 is positioned internally of the fibrous Core 12 suchthat its lateral edges are spaced inwardly at an equal distance fromeach of the lateral edges of the fibrous core 12. Similarly, the ends ofthe fibrous insert 22 are spaced an equidistance from the ends of thefibrous pad 12. By being so positioned internally of the sanitary napkincore 12, the ends of the core where the insert is not located as well asthe longitudinal edges of the core where the fibrous insert 22 is notlocated provide soft, form-fitting edges to the sanitary napkin whilethe fibrous insert at the center, thereof, provides the necessary formstability and because of its corrugations particularly, excellent formstability in the transverse direction while providing for high loftbeing maintained in the napkin during use.

As shown, however, in FIGURE 7, the invention contemplates as well theincorporation of the fibrous insert 22 within a sanitary napkin wherethe lateral edges of the fibrous insert 22 extend all the way to thelateral edges of the fibrous core 12. In this embodiment, the widerfibrous insert assures even greater transverse stability of the sanitarynapkin by way of the corrugations extending throughout the width at thecenter of the napkin core. Particularly in those embodiments employingthe thin, polyethylene, fluid impervious barrier 23 which extendsupwardly over the sides of the absorbent core of the napkin, anyharshness that normally would result from the fibrous insert 22extending all the way to the lateral edges of the core is mostlyobliterated by being covered at the lateral edges by the Polyethylenesheet 20.

In use, an absorbent pad, such as a sanitary napkin employing thelongitudinally embossed and transversely corrugated fibrous insert,provides for excellent transfer of fluids laterally and longitudinallyin the fibrous core 12. The densified, compressed, longitudinallyextending areas 30 are highly effective in transferring the fluidsmpinging at the center of the fibrous core longitudinally therein whilethe lesser compressed transverse corrugations in the fibrous insert areeffective to distribute the fluid laterally in the fibrous core. Inaddition, however, and most importantly, the corrugations combined withthe longitudinally compressed areas provide for excellent transversestability of the fibrous core of short, cellulosic fibers While at thesame time maintaining high loft in the fibrous core of the sanitarynapkin which also consists essentially of the short, cellulosic fibersSuch as wood pulp or cotton linters. This loft stability is effective inpreventing collapse of the fibrous core of the sanitary napkin whenwetted with large quantities of fluid thereby maintaining substantialbulk in the absorbent portion of the sanitary napkin.

While I have described my invention with particular reference to asanitary napkin, it is to be understood that the construction andprinciples described are equally apiplicable to absorbent products ofother types such as absorbent dressings, bandages, diapers and the like.It is also apparent and should be appreciated that the details of suchconstruction as described by way of a preferred or preferred embodimentsmay be more or less modified within the scope of the claims withoutdeparture from the principles of construction or material sacrifice ofthe advantages of the preferred embodiments.

I claim:

1. In a sanitary napkin of fibrous material having a fluid perviousouter cover and an inner core consisting essentially of short,cellulosic fibers of from about 2 to about 5 millimeters in length, saidcover extending beyond the ends of said core to provide attachment tabs,the improvement comprising a fibrous insert disposed within said innercore and consisting also of said short, cellulosic fibers, said insertbeing provided with transversely spaced, longitudinally extending, wetcompressed areas, and being corrugated in longitudinal cross section,said corrugations being compressed to a lesser extent than saidcompressed areas, except where said corrugations are traversed by saidcompressed areas.

2. The sanitary napkin of claim 1 wherein said insert is positionedwithin said absorbent core with its lateral edges spaced equidistantinwardly of the lateral edges of said core.

3. The sanitary napkin of claim 1 wherein said insert is centrallydisposed in said absorbent core and extends transversely to the lateraledges of said absorbent core.

References Cited UNITED STATES PATENTS 1,863,333 6/1932 Heitmeyer128-290 2,419,971 5/1947 Rumpf et al. 161-135 2,622,051 12/1952Hermanson et al. 161-137 3,017,304 1/1962 Burgeni 128-290 3,046,9867/1962 Harwood 128-290 3,375,827 4/ 1968 Bletzinger et al 128-290FOREIGN PATENTS 64,218 11/1955 France.

CHARLES F. ROSENBAUM, Primary Examiner U.S. Cl. X.R. 156-205; 161-133

